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SI7051 with no library

is another I2C temperature sensor from Silicon Labs. I use their other products, like SI7021, which is temparature and humidity sensor. You can get them from Ebay for very little money. I asked for samples of SI7051, which Silicon Labs agreed to send. Few days later they came with FedEx. Very nice! This is body temperature sensor, which is most accurate in ±0.1 °C from +35.8 °C to 41 °C

±0.13 °C: 20.0 °C to 70.0 °C and

±0.25 °C: –40 °C to +125 °C.

And this is still better then 7021 with typ ±0.3°C (±0.4 max) from –10 °C to +85 °C. And gets a bit worse beyond that.

First thing, when I saw sensor was, woow, this is really 3x3mm (ie. small).

Looking through my adapter boards, I couldn't find none that would be ok, either pad spacing was wrong or pads reached to far inward and would make contact with sensor pad, which is connected to GND and would shors pins.

Then I was thinking, ok, I'll make my own board, should be pretty easy. Only to find no program had 3x3mm DFN package in it. Could make my own, but naah. Couldn't be bothered.

At that moment I went to see, how SI7021 is connected, if pins are the same as on SI7051. And sure enough, they were.

I took my how air soldaring station, set it to 250°C, removed SI7021 from one of Ebay boards. Put some flux on 7051 and placed it on board intead of 7021, a bit of how air and.. it was soldered.

Fired up I2C scanner sketch and I saw new sensor at 0x40 (One thing I don't like is that all this sensors have the same and only one address of 0x40)

As far as sketch goes, I found that it doesn't work with the one from si7021, didn't check, but there must be some different registers you read from. Anyway like with Si7021, there is a sketch for Si7051 that uses no additional librarys. As an extra bonus I added serial read, so you can switch from display every reading (every 10ms or so) if you send 0 over serial. But if you send 1, then you first take 150 samples before it is printer back over serial.

Reading are very stable even if you do one time measurement.

And this is just blowing over the sensor, very fast response

SI7051 sketch

SI7051 visits:

How to make it loud - real loud. (230 watts rms into 8 ohms without clipping from 4 ICs. How to match LM3886s for parallel operation, then bridge the matched parallel banks. If you are not familiar with bridging amplifiers (BTL configuration), read the Application Note on bridging listed left in article Application Note on bridging audio amplifiers.